Critical Influence of Size‐Reduction Techniques on Ginger ( Zingiber officinale ) Oil and Its Analogy in Ginger Tea Flavors

Ginger oil, a global commodity rich in diverse mono- and sesquiterpenes, is largely used as the natural flavor, therapeutic, and cosmetic ingredient. This study aimed to investigate the impact of conventional size-reduction techniques (9, 6, and 3 mm slicing, crushing, grating, and grinding) of fresh ginger on its oil and analogize it in ginger tea volatile flavors. A decrease in particle size elevated the oil yield and critically impacted the oil composition. The finer size enhanced the yield of sesquiterpene hydrocarbons (grated/9-mm slices: 8.0-19.0), thus elevating their concentrations (grated/9-mm slices: 2.8-7.7) and overall oil productivity. Their extraction was ineffective, hence incomplete, from thick slices, which improved upon size reduction. However, a reverse trend was observed for the levels of oxygenated monoterpenes (9-mm slices/grated: 1.5-4.1). The extractability and yield of these monoterpenes were maintained throughout, thus reducing their concentrations with decreasing particle size due to an elevated oil productivity. Utilizing this knowledge, a hydrodistillation-based two-step process was developed, enriching sesquiterpene hydrocarbons and oxygenated monoterpenes separately in two oil fractions. Also, the quantity of these volatile flavors in ginger tea followed a similar trend with traditional size-reduction methods (dicing, crushing, and grating). The amount of major sesquiterpene hydrocarbons was elevated by 3.6-9.3 times in the tea of grated ginger compared to diced, while oxygenated monoterpenes maintained a narrow range. Thus, the current study quantitatively correlated size-reduction methods with the volatile flavors in ginger oil and tea. This knowledge will be useful for the efficient hydrodistillation of fresh ginger or enrichment of major terpene classes thereof.